Question

我想更新在线数据库。我已经意识到当我的网络连接到Wi-Fi时，当我按下刷新按钮时数据库会更新，但是当我的网络连接到3g时，数据库可能会也可能不会更新。如果它得到更新，即使我按下刷新按钮也需要很长时间..我认为缓存存在问题，但我不知道如何将缓存放入我的代码中..这是我的代码：

- (void)downloadAtURLString:(NSString *)urlString
{
    NSMutableData *data = [[NSMutableData alloc] init];
    self.activeDownload = data;
    [data release];
    // encode the urlString with percent escapes
    NSString *urlStr = [urlString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    NSURL *url = [[NSURL alloc] initWithString:urlStr];
    NSURLRequest *request = [[NSURLRequest alloc] initWithURL:url];
    NSURLConnection *conn = [[NSURLConnection alloc] initWithRequest:request delegate:self];
    self.urlConnection = conn;
    [conn release], [request release], [url release];
 }

我尝试使用此代码：

NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:urlString] cachePolicy:NSURLRequestReturnCacheDataElseLoad timeoutInterval:30.0];

我收到警告..是cachePolicy正确吗？

Answer 1

你试过这个吗？此示例忽略请求的本地缓存。

- (void)downloadAtURLString:(NSString *)urlString
{
    NSMutableData *data = [[NSMutableData alloc] init];
    self.activeDownload = data;
    [data release];
    // encode the urlString with percent escapes
    NSString *urlStr = [urlString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    NSURL *url = [[NSURL alloc] initWithString:urlStr];
    NSURLRequest *request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringLocalCacheData timeoutInterval:30.0];
    NSURLConnection *conn = [[NSURLConnection alloc] initWithRequest:request delegate:self];
    self.urlConnection = conn;
    [conn release], [request release], [url release];
 }

同时在您的课程中加入NSURLConnectionDelegate并实施delegate functions以获取NSURLConnection的反馈。

数据库未使用3g更新，但可以与Wi-Fi一起使用

1 个答案: